The polyrotaxane is a molecular aggregate having a structure in which a linear molecule slidably passes through ring molecules and the ring molecules are not eliminated due to blocking groups arranged at both ends of the linear molecule. Therefore, the polyrotaxane is called a slide ring material. Various ring molecules and linear molecules have been known and cyclodextrin as the ring molecule and polyethylene glycol as the linear molecule are often used (Patent Document 1).
Patent Document 2 describes a polyrotaxane crosslinked through ring molecules. The polyrotaxane is characterized by having 10 or more repeating units at the crosslinking part and/or having a number average molecular weight of 1000 or more and containing no solvent. As the crosslinking site, a homopolymer of polysiloxane is exemplified. However, the detailed structure and the effect of the crosslinking site are not described.
Patent Document 3 describes an actuator formed by spirally winding a dielectric sheet, in which an electrode layer is provided on opposite surfaces of a dielectric layer having elasticity, to form a cylindrical product and activated by extending and contracting the dielectric layer by applying and stopping applying voltage to the electrodes. JP 5247123 B also describes a dielectric layer including a polyrotaxane, which has Young's modulus lower in a low strain region than in a high strain region. However, only the polyrotaxane using α-cyclodextrin as the ring molecule and polyethylene glycol as the linear molecule is exemplified and no further description is provided.